Sepsis syndrome (sepsis) is an adverse systemic response to infection that includes low blood pressure, rapid heartbeat and respiration, fever, and organ dysfunction associated with compromised blood circulation. Sepsis can occur through infection by Gram-positive bacteria and even fungi and viruses, or as a consequence of secreted toxins. However, the sepsis syndrome occurs commonly in response to lipopolysaccharides (LPS; also known as endotoxin) from Gram-negative bacteria. LPS is a major constituent of Gram-negative bacterial cell wall and is essential for membrane structure and integrity. The portion of LPS that causes shock is the innermost and most highly conserved phosphoglycolipid, lipid A, which acts by inducing robust inflammatory responses. Over the years, many LPS-binding proteins have been identified on monocytes/macrophages and other LPS-responsive cell types. The identification of CD14, a GPI-anchored protein, as a cell-associated LPS binding protein, represents the first step in the understanding of LPS signalling. However, as CD14 lacks a trans-membrane signalling domain, the involvement of accessory receptor was supposed. Quite recently, several members of the highly conserved family of Toll-like receptor (TLR) proteins were identified as the putative co-signalling molecules for CD14. TLR4 may be an LPS signaling molecule as first suggested by the finding that a constitutively active form of TLR4 resulted in activation of LPS-induced NF-κB-mediated signalling. In addition to TLR4, also TLR2 has been implicated in cellular response to LPS. However, analysis of mice with targeted disruptions in their tlr2 or tlr4 genes revealed that TLR4 knockouts, but not TLR2 ones, are LPS unresponsive, whereas TLR2 appears to be essential for the response to other non-LPS bacterial cell wall products. Following the initial host-pathogen interaction there is a widespread activation of the innate immune response, the purpose of which is to coordinate a defensive response involving both humoral and cellular components. Mononuclear cells play a key role in LPS response, releasing pro-inflammatory cytokines and a host of other small molecules. TNFα and IL-1 are the prototypic inflammatory cytokines that mediate many of the cellular events related to LPS exposure. They are rapidly released (30-90 minutes) after exposure to LPS and in turn amplify the inflammatory response. In addition, several other cytokines, including IL-1 and IL-6, are potent inducers of coagulation. Disorders of coagulation are common in sepsis, and in a certain number of cases (30-50% of patients) also evolve in a more severe clinical form, disseminated intravascular coagulation. In sepsis, LPS (or other bacterial components) initiate coagulation cascade through induction of tissue-factor (TF) expression on mononuclear and endothelial cells. TF in turn activates a proteolytic cascade (coagulation cascade), which finally leads to the conversion of pro-thrombin into thrombin, and consequent activation of fibrin. The net result of this sequence of events is the deposition of fibrin clots in small blood vessels with consequent reduction of tissue perfusion, multiple organ failure and, in several cases, death. The robust inflammatory response that occurs in sepsis is usually balanced by an array of regulatory molecules that attempt to restore immunological equilibrium. Counter-inflammatory molecules include cytokine antagonists such as the soluble TNFα receptors and IL-1 receptor, inactivators of the coagulation cascade and anti-inflammatory cytokines, of which IL-10 is the prototype. Despite this, anti-LPS and anti-TNFα antibodies, soluble TNFα receptors, IL-1Ra and corticosteroids have all failed to alter the outcome of septic shock. A slightly success has been achieved with activated protein C, an anti-thrombotic, anti-inflammatory, serine protease activated by thrombin and consumed during sepsis. Levels of activated protein C are inversely correlated with the probability of death from sepsis, and replacement of activated protein C can reduce the relative risk of death during severe sepsis by almost 20%.
However, it is not known at this time of any pharmacological treatment able to efficiently counteract the sepsis. Here, authors describe a new class of potent and selective anti-inflammatory and anti-thrombotic molecules: the glycerophosphoinositols. Glycerophosphoinositols are natural occurring phosphoinositide metabolites produced by the activity of the α isoform of group IV phospholipase A2 (PLA2IVα) through two sequential deacylation reactions. Although elevated levels of glycerophosphoinositols have been historically associated with the expression of oncogenic Ras, these molecules are detectable in all cell types and their production is increased in response to a large variety of stimuli, both pharmacological (e.g. calcium ionophores) and receptor-mediated (e.g. EGF, ATP and norepinephrine). Glycerophosphoinositols are found both within the cell and in the extracellular space, where they are released via a transporter, Glut-2, characterized both in yeast and in mammalian cells. Glycerophosphoinositols have been found to affect a plethora of cellular functions, ranging from inhibition of adenylyl cyclase, with consequent modulation of thyroid cell growth and iodide uptake, to reorganisation of the actin cytoskeleton in fibroblasts.
Recently, authors have reported a new role of glycerophosphoinositols in modulation of immune response (Zizza et al., J Biol Chem. 2012 May 11; 287(20):16849-59; Corda et al., Biochem Soc Trans. 2012 February; 40(1):101-7; Patrussi et al., Cell Signal. 2007 November; 19(11):2351-60). In T-lymphocyte, indeed, exogenously added glycerophosphoinositols synergise with the chemotactic factor, sdf-1α, by increasing the rate of cell migration.
WO 03/087109 refers to glycerophoshoinositol for the treatment of pathologies mediated by the activation or over-stimulation of enzymatic and metabolic G protein associated pathways, as e.g. septical shock.
WO 02/38575 discloses the use of derivatives and analogues of the glycero-phospho-D-myo-inositol optionally O-substituted for the treatment of pathologies mediated by the activation or over-stimulation of PLA2IVα.
Though both WO 03/087109 and WO 02/38575 mention and claim septic shock, no data are provided even merely suggesting the true therapeutic activity of the compounds.
Authors have now found a new mechanism of action for the onset of sepsis, severe sepsis or septic shock related to a Lipopolysaccharide (LPS)-activated tissue-factor (TF) activity. Authors have found that the stimulus by LPS of TLR receptor is not mediated by PLA2IVα. It has in fact been shown that TF activity is inhibited by GPIs but not by pyrrofenone (a classic inhibitor of PLA2IVα) and thus GPIs can be used to treat septic shock by inhibiting TF activity.
US2010/048492 and US2011/224162 refer to the use of glygerophopshoinositol derivatives for the treatment of pathologies related to overexpression of TNFα. The instant invention refers to the LPS activation of a different factor, TF.
Despite such detailed investigations, there is still the need of a safe and effective agent able to treat, prevent or reduce the severity of a symptom of a pathology comprised in the group of: sepsis, severe sepsis, or septic shock.